With the development of mobile systems and various application systems, a demand for flash memory device has increased. The flash memory device is capable of storing data even when no power is supplied. Generally, flash memory cells in the flash memory device are programmed using the tunneling phenomenon. During programming, the Incremental Step Pulse Program (ISPP) method is applied to make the threshold voltage distribution in the flash memory cells dense. In the ISSP method, a program voltage is applied on the flash memory cells, and then the flash memory cells are verified by comparing a threshold voltage with a verify voltage. For flash memory cells having a threshold voltage less than the verify voltage, a new higher program voltage is applied.
The programming operation of the flash memory device is performed as a page unit. At this time, the instant coupling noise may be happened between the selected bit line connected to the program memory cell and the non-selected bit line connected to the program inhibit memory cell. To reduce the peak the instant coupling noise, the flash memory cells are divided into several program blocks, and the program blocks are serially programmed. And, here is a time interval between the program starting points of the program blocks. At this time, due to the accumulation of the time intervals cause, the total program time is increased.